HIV-infected patients commonly develop autonomic neuropathy (HIV-AN), which is a heterogeneous disorder characterized by varying degrees of both sympathetic and vagal dysfunction. We hypothesize that the vagal component of HIV-AN contributes to chronic inflammation, both directly via loss of cholinergic activity, and indirectlyvia effects on the gastrointestinal (GI) tract, and that these effects will be treatable using the acetylcholinesterase inhibitor pyridostigmine. The autonomic nervous system controls the inflammatory response to lipopolysaccharide (LPS) via the cholinergic anti-inflammatory pathway. This pathway is mediated by the vagus nerve, and is therefore likely impaired in HIV-AN with vagal dysfunction. Vagal dysfunction also causes slowed GI transit, which could exacerbate LPS-driven inflammation by promoting bacterial overgrowth. However, the anti-inflammatory impact of cholinergic pathways is almost completely unstudied in HIV, despite the known importance of inflammation in HIV disease progression. Therefore, in this exploratory pilot, we seek to establish associations between vagal dysfunction, GI motility and inflammation in virally suppressed, CART- treated individuals with HIV-AN. Specific Aim 1: To determine whether vagal dysfunction is associated with immune activation in CART- treated participants with HIV-AN, and if so to estimate the extent to which this association is mediated by GI effects (i.e. slowed motility, bacterial overgrowth, microbial translocation) versus direct effects of vaga dysfunction. Specific Aim 2: In a subset of participants who have both vagal and GI dysfunction, to investigate whether 8 weeks of pyridostigmine: a) reduces immune activation, and b) improves GI motility; and if the immune effect depends on the GI effect. To achieve these aims, we will recruit 80-100 participants with HIV-AN and GI symptoms who will be assessed for: vagal dysfunction (heart rate variability); GI dysmotility (gastric emptying scintigraphy); small intestinal bacterial overgrowth (breath testing); microbial translocation (LPS and sCD14); and immune activation (IL-6 and CRP). Participants meeting threshold criteria for both vagal and GI dysfunction will then be treated with pyridostigmine for 8 weeks, after which GI and immune measures will be reassessed.